The role of protein metabolism in the vasculature has been investigated with regard to the pathogenesis of hypertension and stroke in genetic animal models. Our previous observation was that incorporation of amino acids into vascular proteins in young spontaneously hypertensive rats was significantly increased. In an attempt to work with biochemical preparations, we prepared brain microvessels from rats that had been injected with radioactive lysine and examined incorporation into collagen and non-collagen proteins. The incorporation into microvessels was greater on a weight basis than in other small vessels and the SHR exhibited a higher rate of incorporation into collagen than normotensive controls.